The present invention relates to wound dressing materials.
The present invention further relates to transdermal and topical drug delivery device constructions.
The present invention more particularly relates to transparent and absorbent wound dressings which do not adhere to exposed tissues and which may additionally be used to deliver medicaments to the wound site.
The drug delivery devices and wound dressings of the present invention are comprised of hydrophilic polymer blends, which may, for example, comprise compositions such as those described in U.S. Pat. No. 4,300,820 (K. R. Shah) entitled "Water Absorptive Compositions", and U.S. patent application Ser. No. 606,794, filed May 3, 1984 in the name of Kishore R. Shah.
It is accepted in the medical arts that the use of water vapor-permeable, but liquid water and bacterial barrier membranes, on skin wounds is a preferred method of wound healing management.
Indeed, there are numerous patents describing such devices which have employed varying construction materials in order to achieve the desired ends, see e.g. U.S. Pat. Nos. 3,419,006, 3,557,516, 4,413,621, and published European patent application No. 81300847.1.
In general, the prior art devices made from conventional materials may include two broad compositional categories; i.e. those comprised of hydrogels and those comprised of non-hydrogel materials.
Products utilizing non-hydrogel materials offer a number of advantages. Apart from providing generally high tensile strength, water vapor permeability, liquid water and bacterial barrier properties and transparency, these non-hydrogel products are usually utilized in conjunction with a pressure-sensitive, hypoallergenic adhesive which functions primarily to secure the wound dressing in place, thus prohibiting or greatly limiting bacterial contamination when properly applied to the wound site.
However, these prior art non-hydrogel material wound dressings have a number of drawbacks. Firstly, because these non-hydrogel materials are liquid water barriers and therefore non-absorbent, the dressings may become readily detached from the wound application region when an excess of tissue fluid accumulates at the dressing-tissue interface site.
Secondly, administration of medicaments through the liquid water barrier layer film is essentially impossible. Although a number of patents teach the incorporation of drugs into either the adhesive, e.g. U.S. Pat. No. 4,310,509, or the backing, e.g. U.S. Pat. No. 4,340,043, to address this concern, such materials restrict the physicians' choice of drug therapies by offering only a limited selection of incorporated releasable compounds.
Thirdly, these conventional materials do not impart an additional degree of comfort to the patient such as found in the hydrophilic polymer blend devices of the present invention. Although perhaps less painful than traditional gauze dressings, the conventional non-hydrogel polymeric materials are not soothing to the wound area.
Recently, conventional hydrogel-type wound dressing materials have become available which correct some of the disadvantages associated with the non-hydrogel prior art wound dressings. Conventional hydrogels, having a high water content, may permit water-soluble drugs to migrate through the hydrogel film without disruption of its bacterial barrier properties. (See e.g. U.S. Pat. No. 3,419,006.)
Additionally, the conventional extremely soft water-swollen hydrogel material imparts a cooling or soothing sensation upon application to the skin, which is particularly important at inflamed and sensitive areas. However, conventional hydrogel dressings do not readily adhere to exposed wound tissue. Therefore, an additional means of anchoring the dressing to the wound area, so as to maintain an anti-bacterial seal, is required. In addition, some conventional hydrogel materials, being non-thermoplastic, are quite difficult to apply, requiring in situ formation of the barrier film. (see U.S. Pat. Nos. 3,577,516 and 4,287,177.) As a consequence, the cumbersome in situ formation of these conventional hydrogel products creates difficulties in their use.
The present invention provides a hydrophilic laminate composition which is comprised of layers of both pressure-sensitive and non-pressure-sensitive materials, at least the non-pressure-sensitive layer being capable of forming a hydrogel. Preferably, both layers are capable of forming hydrogels. These laminate structures are particularly useful for wound dressings. Such dressings are characterized by high absorbency, strength, mechanical integrity, comfort, transparency, and bacterial barrier properties. Further, these dressings may be utilized in certain drug therapies either by incorporating medicaments into the hydrophilic polymer blend materials prior to application of the dressing to the wound site or by applying the drug to the wound site by penetration through the hydrophilic polymer blends.